iTunes Match, part of the iCloud suite that launched earlier month, stores the entirety of your music library in the cloud, at a cost of $25 per year. Unlike competing cloud storage music services from Amazon and Google, iTunes Match saves a lot of bandwidth and time in your initial synchronization, because Apple can identify which songs in your iTunes library are already available in the iTunes Store. If Apple can positively match a song in your library with any of the 20 million tracks for sale in the iTunes Store, it won’t bother uploading that song; only unmatched songs get uploaded to the cloud.

Once iTunes Match is finished indexing your library, you can connect to your music from other computers, along with your iOS devices. Any matched music you stream from iCloud plays back at 256-Kbps quality—even if your original copy was encoded at a lower quality.

To get started with iTunes Match, fire up iTunes 10.5.1 and look for the new iTunes Match entry in the Store section of the sidebar. Once you subscribe, iTunes Match starts indexing your music right away. You can watch its progress, or continue rocking out to iTunes instead while it does its thing.

Once the initial iTunes Match sync is completed, you’re ready to get started. On your iOS 5 device, go to Settings -> Music and slide iTunes Match to On; then tap Enable when asked to confirm. That’s it—switch to the Music app and, after a few minutes for your iOS device to finish syncing, your iTunes playlists will appear. Songs will download to your device when you play them, and you can also tell the app to download complete playlists or albums.

Apple hasn't yet invited folks with gargantuan music libraries to the iTunes Match party. The service currently includes a 25,000 song limit, although iTunes Store purchases don't count towards the total (assuming they are still available in the iTunes Store, that is); if your library is any larger, you can't sign up for iTunes Match.

I’d love to use iTunes Match, but my iTunes library has more than 25,000 tracks. When I attempt to use the service I’m told that I have too many tracks. Is there any way around this?

There is, but it’s not an entirely scenic route. iTunes Match—at least up to this point—places a hard limit on iTunes libraries. Either you have fewer than 25,000 tracks (not purchased from the iTunes Store, as purchased tracks are not counted against this limit) and everything’s hunky dory, or you have more than 25,000 tracks and you’re barred from the door.

In a perfect world, rather than giving you the boot, iTunes would then offer a suggestion along the lines of “Since your entire iTunes library is too expansive for iTunes Match, would you like to upload some of your favorite playlists?” But it doesn’t. So you must take matters into your own hands. And that means feeding iTunes Match a different library.

Perhaps no part of Apple’s iCloud service has prompted as much interest as iTunes Match. You could attribute that to a number of factors, including Apple’s industry-dominating music store, iTunes Match’s library-matching system, and the fundamental integration with all of Apple’s devices. But in general, I think it’s the idea of having your music everywhere, always at your fingertips, that’s really captured the interest of users.

So you’ve bought iTunes Match, which gives you access to shiny new 256kbps AAC versions of your audio files. But by default your iTunes library is still packed with your old files. So how best to upgrade all of those old files, in place, to the new versions?

Here’s how to do it—keeping in mind that you can only do this after you've completely turned iTunes Match on:

Make a Smart Playlist Create a Smart Playlist with the following attributes:

Bit Rate is less than 256kbps

Media Kind is Music

Any of the following are true: (to create this conditional, option-click on the plus button in the Smart Playlist window) iCloud status is Matched, iCloud status is Purchased

When Apple announced iTunes Match in June as a part of a raft of announcements related to iCloud, I was a little skeptical. I had just been released from my annual $99 payment to Apple for MobileMe, thanks to iCloud—I wasn’t excited about a new annual subscription taking its place.

Perhaps back then the details of iTunes Match weren’t quite clear enough, or perhaps I just wasn’t prepared to understand them. But after having used iTunes Match for a few weeks now, I’ve come to appreciate the service quite a bit… and have accepted that I’ll probably keep paying for it for years to come.

For me, it starts with keeping the integrity of my iTunes library across many different devices. I have an iMac on my desk at work, a Mac mini with all my music on it at home, and a MacBook Air with me just about everywhere I go. Plus an iPad and an iPhone. A lot of the features of iTunes were originally designed for the idea of a single jukebox on a single computer, and it showed. Syncing with iPods and iPhones was okay, but if you had a second Mac somewhere else, things started to fragment quickly. (Take the concept of play counts. I love personal statistics, and the idea of finding out exactly how many times I’ve played a song is great! But listening on a few different Macs—or losing the play count when you delete a song from your iTunes library for some reason—meant that the play count was never meaningful to me.)

With iTunes Match, that stuff—most notably playlists and song metadata—goes everywhere and stays in sync. You could completely delete your iTunes music library on your main computer and then reconstitute it from the cloud, playlists included. As someone who has had to build and re-build playlists over the years, that’s pretty cool.

iTunes Match has entered the public arena (for the U.S., at least), and it’s brought along a rush of questions. Never fear: Macworld is here to help make sense of it all. Here are some of the most common queries, concerns, and misconceptions about Apple’s music service, laid out for your reading pleasure.

iTunes Match basics

What is iTunes Match?

iTunes Match is part of Apple’s iCloud and iTunes in the Cloud initiative (although you do not need an iCloud account to sign up, only an Apple ID associated with iTunes). For $25 a year, the service does two things: match and upload your music library to a central server, and let you download (or stream, if you’re on a computer) those items to devices you own.

I drafted editorial director Jason Snell to help me figure this one out, and we’ve got good news: Any computer that is authorized to play protected iTunes music can add that music to iTunes Match. This is the case even if the Apple ID being used for iTunes Match isn’t the same one that was used to buy the music.

I have an album in my iTunes library that was purchased using a family member’s Apple ID. This album was purchased in the days before iTunes went DRM-free, so every song is a Protected AAC file—that is, they are copy-protected and linked to a single Apple ID. My laptop is authorized to play content purchased by that ID, so I can listen to the song on my computer and on my iPhone; unfortunately, I can’t move it to any other computer of mine (my iMac at work, for example) because that Apple ID has reached its limit of five authorized computers, and protected iTunes music won’t play on computers that are unauthorized.

Enter iTunes Match. When I enabled the service on my laptop, those protected songs showed up with an iCloud Status of Matched. This is the same status iTunes Match uses for songs you’ve ripped from a CD or received from other sources, and it indicates that you can re-download the song again as a DRM-free 256-kbps AAC file.

When you enable iTunes Match on an iOS device (Settings -> Music -> iTunes Match), you'll see a warning that “iTunes Match will replace the music library on this device.” When iTunes Match was still in beta, that message was true to its word: Any music you had on your device was indeed deleted, in favor of the library you'd uploaded to the cloud via iTunes Match. But in the official version of iTunes Match released Monday, that’s no longer the case. In truth, any music that was on your iOS device before you enabled iTunes Match will still be there—and that fact can save you on time and bandwidth.

In our testing, this message is a big fat lie.

After you've enabled iTunes Match, it downloads songs to your iOS device on an as-needed basis: When you tap on an individual song, iTunes Match downloads it first, then starts playing it. (That accounts for the slight delay you'll notice before the track begins; iTunes is buffering the download.) After you've played that song once, the downloaded copy stays on your device. The next time you want to play it, it’ll already be there; it doesn't need to be downloaded again. Tracks that are available via iTunes Match but haven't been downloaded yet are marked with an iCloud icon. Once you tap to play them, that icon disappears.

But those already-played songs aren't the only ones you'll find on your device: Despite Apple’s warning, any songs that you had synced to your device prior to turning on iTunes Match will still be there. They don't display an iCloud icon; your device and iTunes Match are smart enough to recognize that the tracks are already available.

However, after you enable iTunes Match, you can no longer sync music via iTunes; if you try, the Music tab for your device in the iTunes app will indicate that iTunes Match is on and will offer the option of syncing Voice Memos only. So let's say you want to have the $149 complete Beatles anthology —more than 250 tracks—on your iOS device. You bought it some time ago, but never synced it to your iOS device. Now, the only apparent way to get all of those tracks on your device again is to tap on The Beatles from the Artists tab, scroll to the bottom of the albums, and tap Download All. That would seem to be a big waste of time and bandwidth.

iTunes Match has arrived, and it’s the subject of this week’s Macworld Podcast. Senior associate editor Dan Moren, senior editor Christoper Breen, and staff editor Serenity Caldwell have spent the past few days learning all there is to know about Apple’s $25-per-year music service, and they’re ready to drop some iTunes Match-based knowledge on you in the next 28 minutes.

Download Episode #271

Show Notes

Among the icons you might see in your iTunes library after enabling iTunes Match is this unfriendly guy to the left: a cloud with an exclamation point in it. No, it’s not hinting at a chance of inclement weather; it means that iTunes Match has encountered a problem while scanning the track in question.

Of course, iTunes isn’t very helpful about it: Enable the iCloud Status column in iTunes and you’ll simply see “Error”; click on the exclamation-point-bearing cloud icon and you’ll get this “helpful” dialog box.

Generally, what this really means is that there’s a corruption somewhere in the file—it may be one that you can’t even detect by examining the file or even by listening to it.

We’ve told you what you need to know about iTunes Match. But we’re also happy to share with you some secrets of iTunes Match that you don’t absolutely need to know, yet might enjoy knowing anyway. Trust that tucking these tidbits away will make you the star of every party—at least parties where everyone sits around and talks about the nuances of iTunes Match.

Downloaded songs are automatically removed to make extra space

When you tap to play a song on your iTunes Match-enabled iOS device, the song gets cached. That way, if you tap to play, say, “Je Suis Rick Springfield” by Jonathan Coulton on your iPhone today, the song won’t need to get downloaded all over again when you tap to play it again tomorrow. Similarly, you can tap to download complete playlists or albums on your iOS device; maybe you’d do so while on Wi-Fi so that you could hear all of Coulton’s latest album later during your commute home, without gobbling up your data plan.

Of course, one of the benefits of iTunes Match is that you can free up extra space on your iOS devices by not syncing your entire library. Once you start downloading lots of songs as you play them back, does that advantage vanish? In a word: No. In more words: With iTunes Match enabled, your iOS device will automatically remove some downloaded songs over time. The algorithm is smart—older and least-played tracks are removed first.

Apple hasn’t clarified under precisely which circumstances songs get removed. Perhaps one day we’ll see an option to control how much storage space iTunes Match can use for caching on your device, but no such option exists yet. So while you can manually remove tracks from your iOS device by swiping as if to delete them (which leaves the iCloud-stored track in place, but frees up the few megabytes the song requires), it shouldn't be necessary; your device will take care of eliminating old tracks automatically.

The Download column displays icons indicating the current status of your songs. These icons generally appear only when an action is pending or if something has gone awry—such as a song that is ineligible to upload or an error in the uploading process. That’s why, if all has gone well with your initial iTunes Match setup, you should see few if any icons in this column. One exception: a Download icon may appear even though nothing is wrong; I’ll get to this in a bit.